A mechanism called “counter” is used mostly for counting the number of copies in an information processing apparatus such as a copy machine or counting the number of days using software in trial. Generally, in such information processing apparatus, an integral value is used for a counter value to be counted by the counter. The counter value is incremented or decremented for each use according to the embodiments.
In the conventional general techniques, methods below are known as a method for restricting a function of an information processing apparatus by using a counter.
(1) A method for disabling an information processing apparatus when a counter value reaches the upper limit, wherein the information processing apparatus is equipped with a counter mechanism that increments the counter value, and the counter value has the upper limit.
(2) A method for disabling an information processing apparatus when a counter value decrements from an initial value to reach the lower limit, wherein the information processing apparatus is equipped with a counter mechanism that decrements the counter value, and the counter value has the lower limit (e.g., 0).
The upper limit and the lower limit of a counter will be collectively called “limiting value” below.
Method for changing the upper limit or the like of a counter from outside the information processing apparatus equipped with the abovementioned conventional counter mechanism conventionally include methods below.
(1) A screen or the like that is not used by a general user is prepared and a specific user (administrator) sets or changes the current value or the limiting value of a counter on the screen or the like.
(2) License information that cannot be created by a general user is supplied to an information processing apparatus and the information processing apparatus sets or changes the current value or the limiting value of a counter based on the contents of the supplied license information. The method is executed with a method of a digital signature or the like using a private key for preventing a general user from creating license information. A method for restricting a period of service for an information processing apparatus with the abovementioned license information has been known (for example, see Japanese Patent Laid-Open No. 5-197542).
However, among the abovementioned methods of changing a limiting value or the like of a counter from outside, in the first method of preparing a screen that is not used by a general user, processes to reach the setting or changing screen need to be prevented from being leaked to a general user. Thus, the procedure of reaching the screen should be much complicated, which in turn makes management of the information quite troublesome. Even if the information is not leaked, a general user may find out how to manipulate the information. Therefore, the first method is not completely secure.
On the contrary, the latter method of supplying the apparatus with license information is more secure than the abovementioned first method of using a screen, and can be used where advanced security is needed. However, a conventional method of supplying the apparatus with license information including a limiting value of a counter and setting the limiting value of the counter is an operating method which ignores the supplied current value of the counter of the apparatus, lacking flexibility and hard to be operated.
In order to perform a flexible operation, a method of including incrementing information of a counter in license information can be considered. However, even in this method, a general user may use the same license information and repeatedly change the counter value. In order to avoid this risk, the license information needs to include an expiration date or the apparatus needs to record used license information, which makes the method very complicated.
The abovementioned conventional methods have weakness respectively. For example, when license information includes an expiration date, another problem occurs in that a general user who has not made use of a function of the information processing apparatus by the expiration date has to bear an extra cost. As an information processing apparatus has the limit for the number of license information pieces to record, another problem occurs about dealing with license information pieces over the limit when the apparatus records used license information.
An information processing apparatus in which a limiting value of a counter for restricting the use of the apparatus can be dynamically set and changed in a secure method and a controlling method of the information processing apparatus.